Vulnerability Monitor

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CVE-2026-21921


A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS). When telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered. This issue affects:  Junos OS:  * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2; Junos OS Evolved: * all versions before 22.4R3-S8-EVO, * 23.2 versions before 23.2R2-S5-EVO, * 23.4 versions before 23.4R2-EVO.


Security Impact Summary

This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction requiring only low-level privileges . The vulnerability impacts and availability (service disruption) for affected systems. Impacting 2 products from juniper, from juniper organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2026, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.


Published

2026-01-15T21:16:08.400

Last Modified

2026-01-23T18:52:35.070

Status

Analyzed

Source

[email protected]

Severity

CVSSv3.1: 6.5 (MEDIUM)

Weaknesses
  • Type: Primary
    CWE-416

Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Operating System juniper junos < 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 22.4 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.2 Yes
Operating System juniper junos 23.4 Yes
Operating System juniper junos 23.4 Yes
Operating System juniper junos 23.4 Yes
Operating System juniper junos 23.4 Yes
Operating System juniper junos_os_evolved < 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 22.4 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.2 Yes
Operating System juniper junos_os_evolved 23.4 Yes
Operating System juniper junos_os_evolved 23.4 Yes
Operating System juniper junos_os_evolved 23.4 Yes
Operating System juniper junos_os_evolved 23.4 Yes

References

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For juniper's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.